or most of the
weight of the robot
will be on powered
wheels, maximizing
the pushing power
and acceleration of
the robot. Four wheel
drive robots will have
a bit more trouble
turning than two
wheel drive robots
due to the wheels
skidding sideways
while the body of the robot turns. A
wider wheelbase reduces the effect
and makes it behave more like a
two wheel drive robot. The difficulty
turning, however, is balanced by it’s
increased ablity to drive in a straight
line. You should choose four wheel
drive if: your design needs to use
the entire weight of your robot for
traction; needs to have powered
ground contact at all corners; or
doesn’t need to be as light as
possible.

Doom On You uses its four driven wheels to put a lot
of power on the ground and allow it to move around
the arena quickly, choosing when and where it hits
its opponents.

Shovelhead uses all six wheels to get
the incredible drive power it has on the
ground, allowing it to use both its bulk
and wedge as weapons.

Tracked Drive

Six Plus Wheel Drive

Robots with six or more wheels
behave much like four wheel drive
robots. They have the same issues
with turning and the same benefit
to driving in straight lines. One
common variation is to have the
central wheels lower than the front
or rear wheels by 1/8”-1/4” which
causes the body to rock back and
forth, essentially becoming a four
wheel drive robot with a relatively
wide wheelbase. Six wheel drive
increases the number of contact
points with the arena floor, making
it even harder to be high centered in
a match. The increased number of
wheels also allows the use of
wheels with softer treads as each
wheel will not wear as fast due to
the reduced forces on the tread.

You should choose six or more
wheel drive if your design needs
more ground contact than a four
wheel drive robot or if you need
more than four wheels to
properly transmit the power from
your motors to the ground.

Tracked drives are not very
common in robot combat due to
the increased weight and fragility of
the system. Tracks are a large target
on any robot with them. They either
have to be well protected or built to
handle direct weapon blows to survive well. Track systems have a huge
contact patch and are much less
likely to get hung up on anything in
the arena. Well-built tracks can be
very effective, but are difficult to
make and often very complex compared to wheeled drive systems. You
should choose tracked drive if your
design needs maximum ground contact or if you are placing style over
efficiency in your drive train design.

Omni Drive

Omni drives are a simple way
to allow your robot to strafe.
Strafing is when the robot is able
to move to the left or the right,
essentially driving sideways.
Depending on the number of
wheels — typically either three or
four — they are normally placed 90
or 120 degrees apart to keep

the spacing between them even.
The wheels themselves have rollers
built into them. This provides friction
in the direction the wheel spins
while having almost no friction
when moving side to side. Different
combinations of speed controller
commands will allow the robot to
move in all the normal directions,
as well as side to side and at odd
angles. The main disadvantage of
this is that the robot will not be able
to push as well as if it had solid
wheels and that the movement
speed is reduced due to wheels
being so heavily angled. You will
likely need a specialized electrical
control mixer or to learn how to
program the mixing into your
transmitter to drive an omni wheeled
robot effectively. You should choose
omni drive if your design needs to
strafe but you don’t want to pay for
or make mecanum wheels.

Mecanum Drive

Mecanum drive is a variant on
the standard omni wheel. Instead of
the wheels being at angles, the
rollers inside the wheel are angled

Phantasm uses the strafing ability
its wheels provide to maneuver
quickly in any direction while still
being able to keep the flipping arm
pointed at its opponent.

Jawbreaker Jr.
uses the tracks to
put as much pushing
power behind its low
wedge as possible.